Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology
The subglacial environment of the Greenland Ice Sheet (GrIS) is poorly constrained both in its bulk properties, for example geology, the presence of sediment, and the presence of water, and interfacial conditions, such as roughness and bed rheology. There is, therefore, limited understanding of how...
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ftcopernicus:oai:publications.copernicus.org:tc75652 2023-05-15T16:28:15+02:00 Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology Cooper, Michael A. Jordan, Thomas M. Schroeder, Dustin M. Siegert, Martin J. Williams, Christopher N. Bamber, Jonathan L. 2019-11-26 application/pdf https://doi.org/10.5194/tc-13-3093-2019 https://tc.copernicus.org/articles/13/3093/2019/ eng eng doi:10.5194/tc-13-3093-2019 https://tc.copernicus.org/articles/13/3093/2019/ eISSN: 1994-0424 Text 2019 ftcopernicus https://doi.org/10.5194/tc-13-3093-2019 2020-07-20T16:22:33Z The subglacial environment of the Greenland Ice Sheet (GrIS) is poorly constrained both in its bulk properties, for example geology, the presence of sediment, and the presence of water, and interfacial conditions, such as roughness and bed rheology. There is, therefore, limited understanding of how spatially heterogeneous subglacial properties relate to ice-sheet motion. Here, via analysis of 2 decades of radio-echo sounding data, we present a new systematic analysis of subglacial roughness beneath the GrIS. We use two independent methods to quantify subglacial roughness: first, the variability in along-track topography – enabling an assessment of roughness anisotropy from pairs of orthogonal transects aligned perpendicular and parallel to ice flow and, second, from bed-echo scattering – enabling assessment of fine-scale bed characteristics. We establish the spatial distribution of subglacial roughness and quantify its relationship with ice flow speed and direction. Overall, the beds of fast-flowing regions are observed to be rougher than the slow-flowing interior. Topographic roughness exhibits an exponential scaling relationship with ice surface velocity parallel, but not perpendicular, to flow direction in fast-flowing regions, and the degree of anisotropy is correlated with ice surface speed. In many slow-flowing regions both roughness methods indicate spatially coherent regions of smooth beds, which, through combination with analyses of underlying geology, we conclude is likely due to the presence of a hard flat bed. Consequently, the study provides scope for a spatially variable hard- or soft-bed boundary constraint for ice-sheet models. Text Greenland Ice Sheet Copernicus Publications: E-Journals Greenland The Cryosphere 13 11 3093 3115 |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
The subglacial environment of the Greenland Ice Sheet (GrIS) is poorly constrained both in its bulk properties, for example geology, the presence of sediment, and the presence of water, and interfacial conditions, such as roughness and bed rheology. There is, therefore, limited understanding of how spatially heterogeneous subglacial properties relate to ice-sheet motion. Here, via analysis of 2 decades of radio-echo sounding data, we present a new systematic analysis of subglacial roughness beneath the GrIS. We use two independent methods to quantify subglacial roughness: first, the variability in along-track topography – enabling an assessment of roughness anisotropy from pairs of orthogonal transects aligned perpendicular and parallel to ice flow and, second, from bed-echo scattering – enabling assessment of fine-scale bed characteristics. We establish the spatial distribution of subglacial roughness and quantify its relationship with ice flow speed and direction. Overall, the beds of fast-flowing regions are observed to be rougher than the slow-flowing interior. Topographic roughness exhibits an exponential scaling relationship with ice surface velocity parallel, but not perpendicular, to flow direction in fast-flowing regions, and the degree of anisotropy is correlated with ice surface speed. In many slow-flowing regions both roughness methods indicate spatially coherent regions of smooth beds, which, through combination with analyses of underlying geology, we conclude is likely due to the presence of a hard flat bed. Consequently, the study provides scope for a spatially variable hard- or soft-bed boundary constraint for ice-sheet models. |
format |
Text |
author |
Cooper, Michael A. Jordan, Thomas M. Schroeder, Dustin M. Siegert, Martin J. Williams, Christopher N. Bamber, Jonathan L. |
spellingShingle |
Cooper, Michael A. Jordan, Thomas M. Schroeder, Dustin M. Siegert, Martin J. Williams, Christopher N. Bamber, Jonathan L. Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology |
author_facet |
Cooper, Michael A. Jordan, Thomas M. Schroeder, Dustin M. Siegert, Martin J. Williams, Christopher N. Bamber, Jonathan L. |
author_sort |
Cooper, Michael A. |
title |
Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology |
title_short |
Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology |
title_full |
Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology |
title_fullStr |
Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology |
title_full_unstemmed |
Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology |
title_sort |
subglacial roughness of the greenland ice sheet: relationship with contemporary ice velocity and geology |
publishDate |
2019 |
url |
https://doi.org/10.5194/tc-13-3093-2019 https://tc.copernicus.org/articles/13/3093/2019/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-13-3093-2019 https://tc.copernicus.org/articles/13/3093/2019/ |
op_doi |
https://doi.org/10.5194/tc-13-3093-2019 |
container_title |
The Cryosphere |
container_volume |
13 |
container_issue |
11 |
container_start_page |
3093 |
op_container_end_page |
3115 |
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1766017889997946880 |